Subject: MP Protocol reject after negotiating MP?

From: [email-masked]
Date: Wed, 27 Sep 2000 17:33:22 -0400

Folks,

I am seeing a unexpected response from an ISP when I attempt to negotiate
the Multilink Protocol with it. I expect I'm dealing with an old (or just
stupid) MP implementation, but want to better understand the situation.

My peer calls the ISP and successfully negotiates LCP over 2 links. For
both links the MRRU option is successfully negotiated on both sides of the
link for both links so the ISP agrees to use multilink. However, if my peer
sends an (MP encapsulated) IPCP over the 2'nd link, the peer responds with
a protocol reject for the MP protocol, 0x003D. When the NCP packets are
only sent over the first link, then the peer does not reject them and IPCP
negotiation completes successfully.

After IPCP negotiation has completed we can send MP encapsulated IP packets
over both links.

Do most MP implementations tolerate/expect this type of behavior from a
peer? That is, is it an accepted practice to limit the sending and
receiving of NCP packets to the first link of an MP bundle?

P.S. I vaguely remember this topic being mentioned in James Carlson's "PPP
Design & Debugging", but couldn't find it again. If someone could forward
me the page number to look at, I'd appreciate it.

Thanks,

-john martz, 8-852-5539,  [email-masked]
IBM AS/400 TCP/IP PPP development (and stuff)

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From: James Carlson <[email-masked]>
Date: Wed, 27 Sep 2000 17:47:23 -0400 (EDT)

> negotiation completes successfully.

I vaguely recall seeing this with Ascend equipment.  It was over five
years ago, so I might be sorely mistaken.  In any event, you're right.
This behavior is wrong.  As soon as you reach the point where you
would have gone to Network phase (authentication, if any, is done),
you're in the bundle.  Links in the bundle are *not* distinguished in
this way.

(It's also wrong in that you should never send LCP Protocol-Reject
unless you're refusing to run that protocol for all time on that link.
If you send it just because you're not ready for that protocol, but
you might be ready later, then that itself is another bug.)

> receiving of NCP packets to the first link of an MP bundle?

Yes and no.  Most implementations dial only on demand, so the first
link (along with all of the NCPs) is long established by the time the
second link comes up.  Some can be told to dial all links at once,
and, yes, these will have trouble with a misbehaving peer.

> me the page number to look at, I'd appreciate it.

Sigh.  I forgot to mention this problem, and I clearly should have.

-- 
James Carlson                                  <[email-masked]>
"PPP Design and Debugging" --- http://people.ne.mediaone.net/carlson/ppp

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From: Archie Cobbs <[email-masked]>
Date: Wed, 27 Sep 2000 15:37:22 -0700 (PDT)

> you're in the bundle.  Links in the bundle are *not* distinguished in

I can independently confirm this behavior; we first reported it
several months ago. I've seen it with Ascend/Lucent equipment only.
As far as I know, they haven't fixed this bug yet.

-Archie

___________________________________________________________________________
Archie Cobbs   *   Whistle Communications, Inc.  *   http://www.whistle.com